Processes for producing photographic images and elements therefor



=cyanine pigment. process which is simple and dependable. -A further ob- United States Patent 2,915,392 PROCESSES FORPRODUCING PHOTOGRAPHIC LIMAGES AND ELEMENTS THEREFOR Charles John 'Pedersen, Salem, N.J., assignor to E. I. du Pont de Nemours and Company, Wiimington, Dei., a corporation of Delaware No Drawing. Application April 20, 1955 Serial No. 502,737

2 Claims. '(CI. 96-27) i'T hisinvention relates to photography and more particularly to a process for producing photographicimages 1n the form of phthalocyanine pigments. The invention also relates to photographic elements, e.g., -filr"ns, foils, plates or papers having at least one light-sensitive Stratum :comprising a solvent-soluble phthalocyanine intermediate complex.

An object of this invention is to provide a new process for producing photographic images in the form of an insoluble phthalocyanine pigment. A more specific object is to provide a new process for producing photographic images in the form of an insoluble metal phthalo- Another object is to provide such a ject is to provide new photographic elements which can be readily processed to yield insoluble phthalocyanine :pigment images. Still other objects will be apparent from ithe'following description of the invention.

It has been found that photosensitive elements "can be prepared by applying on the surface of a suitable support, e.g., a self-supporting film, foil, plate, paper or cloth,'or a laminated sheet made of one or more of such materials, an organic solvent solution of a solvent-soluble phthalocyanine intermediate complex (hereinafter "sometimes referred to as a'leuco-phthalocyanine) and a .light-activatable reducing carboxylic acid or salttaken .R and Rf, as indicated above, may be the same or different and generally should not contain more than 14 carbon atoms.

Among the useful compounds covered by the formula C(OEDGOOQ RI! are glycolic, glyceric, lactic, 'u-hydroxyisobutyric, tartaric, citric, mandelic, benzylic, atrolactic, gluconic, saccharic, mannonic, rn'ucic and tal'omucic acids and their "sodium'and potassium and ammonium salts. -Mixtur'es of any two or more of such salts or acids can be used.

If desired, the surface of the support, particularly if it has hydrophobic properties, can be provided with a layer of a'wa'tenpermeable colloid, e.g., gelatin, polyvinyl alcohol, apdlyvinyl acetal, etc. Such a layer will absorb or imbibe the solution of the complex and the reducing acid ice or sa'lt and, upon processing the-element, will serve as a carrier for the resulting photographic image.

The solvent solution of solvent-soluble phthalocyanine intermediate complex and the reducing acid or salt can be admixed with an aqueous solution or dispersion of a water-permeable colloid and the resulting dispersion 'coated on the surface of a support to form a photosensitive layer, which is dried.

The photosensitive element is exposed through 'a suitable continuous tone, halftone, or line negative to a source of actinic light and treated (a) with a solvent for the leuco-phthalocyanine or (b) with a solution of a strong acid containing water whereby a positive image in the form of a metal phthalocyanine pigment is produced. The image-bearing element is then washed with water and dried.

One type of solvent-soluble phthalocyanine intermediate complex, which has been defined as a precursor, is believed to consist of 1.5 molecules of phthalocyanine, the half molecule being perpendicular in special relationship to the planar structure of the basic phthalocyanine molecule. This complex or precursor has the empirical formula Q(C H.,N NH in which each of the six C H N vgroups represents one phthalonitrile unit, four of which are joined to Q which is two hydrogen atoms -or a central bivalent metal taken from the group consisting of Ca, Ni and Cu, the two extra phthalonitrile units and the extra NH group representing the precursor wing or divalent radical (C H N NH, said com- .plex being further characterized by yielding a metalfree, or a nickel or copper phthalocyanine, repectivel-y,

upon being treated with reducing agents, the remaining two units of phthalonitrile and the extra NH group being split off in the process and in the form of an ammonia and phthalonitrile or other phthalic compound resulting from the interaction of 'phthalonitrile, ammonia and the reducing medium. Considering that the metalphthalocyanine molecule generally consists of 4 phthalonitrile units joined together to a central bivalent metal atom, it is clear that the metal phthalocyanine precursors embrace in their structure a molecule of a metal phthalocyanine plus two extra phthalonitrile units and an extra N'H group. The complexes in question have a structure like that given in col. 2, lines 2 to 18 of Barnhart et a1. U .8. Patent 2,772,284. This type of complex and processes of preparing various complexes are described in Barnhart and Skiles US. application Ser. No. 252,401

filed October 20, 1951 (U.S. Patent 2,772,284, patented Nov. 27, 1956), "and in French Patents 1,068,092, De-

.llVI', February 3, 1954, and 1,094,376, Delivr, December 8, 1954. These solvent-soluble phthalocyanine intermediate "complexes are obtained by reacting, in an alcoholic solvent, a phthalonitrile, ammonia and an anhydrou'ssalt of a metal of the group consisting of copper and 'nickel, 'said complexes being characterized by yielding upon reduction a metal phthalocyanine, a phthalo- 'nitrile and ammonia.

Another type of solvent-soluble pathalocyanine intermediate coi'nplex, more specifically defined as a propigment, can be represented by the formula:

wherein MPc designates the phthalocyanine compound of the group consisting of metal phthalocyanines and Co, Ni, Cr, Fe, Mg and Na. These complexes are obtained according to the procedures described in Pedersen US. 2,662,895 and 2,662,896.

Yet another type of solvent-soluble phthalocyanine propigment can be represented by the formula:

O-C OR MPc O-COR wherein MPc designates the molecule of a phthalocyanine compound of the group consisting of metal-phthalocyanines and metal-free phthalocyanines, while COR designates the acyl radical of an organic carboxylic acid having a total of not less than 2 and not more than 7 carbon atoms.

These propigments and detailed methods of preparing them are described in Pedersen US. Patents 2,662,895, 2,662,896 and 2,662,897. Moreover, they have a structure similar to that described above for the complexes containing 1.5 molecules of phthalocyanine except that the wing or divalent radical (C H N NH is replaced by two monovalent radicals -OR and -X and -OCOR and -OCOR, respectively, which radicals are defined in the latter two formulae above for the propigments in question.

Each of the solvent-soluble phthalocyanine intermediate complexes described above, for convenience, have been referred to as leuco-phthalocyanines, by analogy to the term employed in the vat dye field, it being remembered, however, that whereas a leuco vat compound is a reduction product of the dye, the leuco-phthalocyanines are in a sense a higher oxidation stage than the corresponding phthalocyanines, inasmuch as they yield the latter upon treatment with reducing agents.

These leuco-phthalocyanines are essentially colorless as compared with the insoluble parent phthalocyanines (which have an intense reddish-blue to greenish-blue color). The leuco-phthalocyanines are barely colored (producing in solution a yellow-brown, or reddish-brown or violet color) and they have no tinctorial value.

As compared with the generally highly insoluble phthalocyanine parent materials, the leuco-phthalocyanines are readily soluble in common organic solvents, e.g., methanol, ethanol, chloroform, acetone, 2-ethoxy ethanol, ethylene glycol monomethyl, monoethyl or monobutyl ether, benzene, toluene and xylenes. They are insoluble in water.

While the exact nature of the colorant-producing reaction is not known, it is believed that the weak reducing action of the reducing acid or salt is augmented by the ultraviolet light to permit reduction of the leucophthalocyanine (precursor or propigment). In general, the reducing acid or salt is used in molecular excess. Good results can be obtained with 1 to 10 mols of the reducing acid or salt per mol of leuco-phthalocyanine.

Prior to use, the photosensitive solutions and photosensitive elements should be kept under conditions of darkness and during use should not be exposed to any significant amount of actinic light. The usual darkroom safelights can be used to prevent undesirable exposure.

The period of exposure will, of course, depend upon H the intensity of the light source, the particular leucophthalocyanine and the particular reducing agent. In general, a period of 0.1 to 10 minutes is required to give an image of satisfactory intensity.

Removal of the leuco-phthalocyanine from the unexposed areas and underexposed portions of the original photosensitive layer can be accomplished by the use of any solvent for the leuco-phthalocyanine. When acids are used in the bath for removing the unexposed areas, a variety of aqueous acid solutions can be used. Suitable such acids include hydrochloric, hydrofluoric, fluosilicic, sulfuric, organic sulfonic, phosphoric, partial esters of Example 1 Four solutions, A, B, C and D, were prepared as follows:

A. Four and one-half grams of the copper phthalocyanine propigment CuPc(Cl),,(OCH as obtailed according to Example 4 of Pedersen US. Patent No. 2,662,896, were dissolved in 150 cc. chloroform at room temperature and the solution was clarified by filtration.

B. Two and one-half grams of oxalic acid dihydrate were dissolved in 300 cc. of a saturated solution of the propigment used in solution A in methanol at room temperature.

C. Fifty cc. concentrated hydrochloric acid (37% HCl) were mixed with 150 cc. methanol and 150 cc. water.

D. Two percent aqueous ammonia.

A Whatman No. 1 filter paper was dipped in solution A and hung up to dry for 5 minutes. It was then dipped in solution B and dried for 15 minutes. Both treatments, A and B, were performed in a dark room at room temperature. The dull yellow colored paper thus prepared was exposed to direct sunlight for 6 minutes under a contrasty photographic negative placed under a piece of window glass. The dull yellow hue changed to green on exposure to sunlight. The exposed paper was immersed in solution C for 1 to 5 minutes, until the yellow colored portion disappeared. The acid decomposed the unreacted propigment, leaving the blue copper phthalocyanine positive print on the paper. The blue positive print was washed in solution D, then in water and dried.

As an alternate procedure the print, after exposure to sunlight, was developed by dissolving away the unreacted propigment with acetone prior to treatments with solutions C and D.

Example 2 Solution E-l was prepared by dissolving 1 gram of the metal-free phthalocyanine precursor (or leuco calcium phthalocyanine) as obtained in Example 2 of Brooks U.S. Patent No. 2,681,348 in grams acetone.

Solution E-Z was prepared by dissolving 2.5 grams oxalic acid dihydrate in 300 cc. methanol.

Working in subdued daylight, a piece of filter paper was dipped in solution E-l and after drying in the air for 5 minutes, was dipped in solution E2 and dried in the air for 15 minutes. The paper was then covered with a piece of glass on which a design had been sketched with a black crayon and was then exposed (about 5 to 10 minutes) under a 275 watt General Electric Reflector Sun sunlamp until the yellow color disappeared. The paper was then treated in solutions C and D as described in Example 1. The metal-free phthalocyanine pigment in the image of the design thus obtained was greenishblue in hue.

Example 3 Solution F was prepared by dissolving 0.05 gram of nickel phthalocyanine propigment, as obtained from NiPc and tertiary butyl hypochlorite according to Example 3 of Pedersen US. Patent 2,662,895, and 0.05 gram of oxalic acid in 5 cc. methanol.

Working in subdued daylight, a sheet of filter paper was dipped in solution F and, after drying in the air for 5 minutes, was dipped in solution E-2 and then dried in the air for 15 minutes. The paper was then covered lamp located 11 inches from the paper.

developed with solutions C and D as described in'Example 1- and the portion that had been exposed .to light was green in hue.

with a piece of glass on which a design had been sketched using a black crayon and exposed for 105 minutes under a 275 watt General Electric Reflector Sun" sunlamp. located 11 inches from the paper. The print was then developed by dissolving away the unreacted propigment with chloroform. The hue of the nickel phthalocyanine pigment in the imageof the design was a greener blue than that obtained inExample 1 withcopper phthalocyanine.

Example 4 Solution G was prepared by dissolving 1 gram of dodecachloroleuco-calcium phthalocyanine. and 0.8 gram of oxalic acid in 100' grams'of acetone. Said leuco compound was prepared from phthalonitrile, ammonia and calcium oxide by the method of Example 1 of Brooks US. Patent 2,681,348, except that 99 parts of 4,5-dichlorophthalonitrile was used instead of the 64 parts of phthalonitrile in the Brooks example.

A sheet of filter paper was treated with the leuco phthalocyanine and oxalic acid solution G, dried, dipped into solution E-2 and again dried according to the procedure described in Example 3. After covering a portion of the treated paper it was exposed for 105 minutes under the 275 watt General Electric Reflector Sun sun- The print was l Example 5 and further processed in solutions C and D as in Example 1. The print obtained contained a positive image-which was blue in hue.

Example 6 Example 5 was repeated except that solution Iwas replaced by a solution of 2.5 grams of mandelic acid in 100 cc. water. The photo-reduction was even faster than that of Example 5. Similar results were obtained in both of these examples.

Example 7 Example 6 was repeated with mandelic acid and benzilic acid as photoreducers. The exposed and developed papers showed clear pictures, although the one prepared with benzilic acid had higher density and contrast than the one prepared with mandelic acid.

Example 8 Example 5 was repeated except that solution I was replaced by a solution of 2.5 grams of atrolactinic acid in 100 cc. water. The print obtained was similar to the one produced in Example 5.

When the ammonium salt of atrolactinic acid was used instead of the free acid in this example, similar results were obtained.

Example 9 Under conditions of subdued light, a piece of Dacron fabric made from polyethylene terephthalate filament fibers was dipped into a saturated solution of sodium chromate in methanol, removed from the solution and dried. The fiber was then dipped into solution H, then dried and finally it was dipped into solution I of Example 5 and dried. The fiber was then partly covered with ob- 1y white.

jects impervious to light and exposed for 5 minutes at a Example 10 While operating in subdued light, a piece of cotton cloth was dipped into a solution of 1 gram of the copper phthalocyanine precursor of Example 5 dissolved in a mixture of 25 ml. of chloroform and 25 cc. of methanol. After air-drying, the cloth was impregnated with a 1% aqueous solution of ammonium acid oxalate. Excess moisture was pressed out and the cloth was placed between two pieces of glass, the top glass bearing a design drawn with a black crayon. Said assembly was exposed to direct sunlight for 5 minutes. The cloth was then removed, dipped into solution C of Example 1 for one-half minute, rinsed thoroughly in water, neutralized with dilute aqueous ammonia and dried. A blue design of copper phthalocyanine was obtained on the cloth.

This example was repeated except that the cotton cloth was replaced by a piece of silk cloth. Again, the process was applied to a piece of cotton cloth that had been dyed yellow with a fast dye. The result was a blue image on a yellow background.

Example 11 The solutions were prepared as follows:

A. One (1) gram of copper phthalocyanine precursor of Example 5 was dissolved in 50 cc. of chloroform.

B. Eight thousandths (0.008) gram molecular weight of glycolic acid in 20 cc. of methanol.

C. Fifty (50) ml. concentrated hydrochloric acid (37% HCl) in cc. of methanol and 150 cc. of water.

While working in subdued light, a sheet of filter paper was dipped into solution Afor 5 minutes. The paper was then removed and air-dried in the dark for 30 minutes. The reducing acid was then applied to the dried paper by pressing onto the latter a sheet of filter paper that Was soaked with solution B. The original paper was then dried in the dark, placed in a cut-out masked frame and exposed to direct sunlight at about 10 oclock in the morning for 2 minutes. The paper was then removed from the frame, dipped into solution C for 5 minutes, then rinsed in water, neutralized with dilute aqueous ammonia and finally dried.

Similar results were obtained by substituting an equivalent amount of lactic, a-hydroxyisobutyric, tartaric and citric acid, respectively, for the glycolic acid of Example 11.

Various light sources can be used as the source of radiation. Suitable sources in addition to sunlight include carbon arcs, mercury vapor arcs, fluorescent lamps with special ultraviolet light emitting phosphors, argon glow lamps and photographic flood (incandescent) lamps. These light sources emit light in the range 1800 to 7000 A. and emit an appreciable amount of radiation at wavelengths of 3000 to 4800 A. which are believed to be the most effective wavelengths. They can be used at various distances but generally are used at distances 7 to 20 inches from the surface of the layer to be exposed.

An advantage of the invention is that it provides new photosensitive elements whereby permanent colored images can be obtained. Another advantage is that it provides practical processes for producing photographic images in the form of phthalocyanine pigments, which images are exceptionally fast to light. A further advantage. is that the invention is simple and practical and does not wherein M represents a metal of the group consisting of copper, nickel and calcium, and A and B together represent the bivalent grouping said compound being characterized by yielding the copper, nickel and metal-free phthalocyanine, respectively, phthalonitrile and ammonia upon being treated with re- :lucing agents, and (b) such a compound represented by the first formula of clause (a) wherein M represents a divalent atom taken from the group consisting of Cu, Fe, Co, Ni, Cr and two hydrogen atoms, and A and B stand for OCOR groups wherein CORis the acyl radical of an organic carboxylic acid of 2' to 7 carbon atoms, and (2) a reducing compound taken from the group consisting of oxalic acid and alpha-hydroxycarboxylic acids and their alkali metal and ammonium salts, and removing said complex in the unexposed and underexposed areas of said layer@ 2. A processs which comprises exposing through an image-bearing transparency by means of light containing a substantial amount of radiations of wavelength between 3,000 and 5,000 A. a layer containing (1) an ethanolsoluble phthalocyanine complex having the formula wherein M represents a divalent atom taken from the group consisting of Cu, Fe, Co, Ni, Cr and two hydrogen atoms, X is a halogen taken from the group consisting of chlorine and bromine and OR is an alkoxy radical, and (2) a reducing compound taken from the group consisting of oxalic acid and alpha-hydroxycarboxylic acids and their alkali metal and ammonium salts, removing said complex in the unexposed and underexposed areas of said layer.

, References Cited in the file of this patent UNITED STATES PATENTS 12,193,574 Tendeloo Mar. 12, 1940 2,683,643 Baumann et al. July 13, 1954 2,772,284 Barnhart et a1. Nov. 27, 1956 OTHER REFERENCES Anthonys Photographic Bulletin, vol. XXIX, 1898, page 329 (pub. Anthony and Co., New York, N.Y.). (Copy in S.L.). 

2. A PROCESS WHICH COMPRISE EXPOSING THROUGH AN IMAGE-BEARING TRANSPARNCY BY MEANS OF LIGHT CONTAINING A SUBSTANTIAL AMOUNT OF RADIATIONS OF WAVELENGTH BETWEEN 3,000 AND 5,000 A. A LAYER CONTAINING (1) AN ETHANOLSOULUBLE PHTHALOCYANINE COMPLEX HAVING THE FORMULA 